文件 Stream：Elixir

Question

I often see in Elixir forums:

"path/to/file"
|> File.stream!(read_ahead: 100_000)

What does read_ahead: 100_000 mean?

Answer 1

It is one of stream_mode 's. It's meaning is described in erlang documentation:

{read_ahead, Size} Activates read data buffering. If read/2 calls are for significantly less than Size bytes, read operations to the operating system are still performed for blocks of Size bytes. The extra data is buffered and returned in subsequent read/2 calls, giving a performance gain as the number of operating system calls is reduced.